Words are not containers that keep one meaning forever. They are habits shared by speakers, and habits drift. Awful, nice, broadcast, mouse and viral each show a different route by which new contexts reshape old vocabulary.
Words are not permanent labels attached to permanent ideas. They are habits shared by communities, and habits change. A word may acquire a new use, lose an old one, become more approving or more insulting, or move from a physical object to an abstract concept. These shifts are called semantic change.
Broadening: a word covers more
Broadening occurs when a word expands beyond an earlier, narrower meaning. Holiday was historically connected with a holy day; it now refers more generally to time away from ordinary work or to a journey taken for pleasure. Business once centred more directly on the state of being busy and now covers organised commercial activity as well as matters requiring attention.
Broadening often happens because one use becomes so common that speakers stop feeling the older boundary.
Narrowing: a word becomes more specific
Narrowing occurs when a word that once covered a wider category comes to name a smaller part of it. Old English deor could refer to an animal more generally; modern deer names a particular family of animals. Meat once had the broader sense of food before becoming restricted mainly to animal flesh.
A narrowed meaning does not make the old use illogical. It shows which distinctions later speakers found useful.
Amelioration and pejoration
Amelioration is a shift towards a more favourable meaning or status. Pejoration is a shift towards a more negative one.
The history of silly is often used to illustrate a long pejorative path. Earlier senses included ideas associated with happiness, blessedness or innocence; later uses moved towards weakness and foolishness. The changes occurred gradually and the exact stages belong to different periods, which is why one-line etymologies can oversimplify.
Social power can drive these changes. Words for groups, occupations or behaviour may gather approval or contempt according to the attitudes surrounding the people they describe.
Metaphor: a familiar shape for a new idea
Many new meanings begin as metaphors. A branch of knowledge resembles a branch growing from a larger structure. An argument has a foundation. A person can grasp an idea. Repeated metaphorical use can become so ordinary that speakers no longer notice the image.
Technology accelerates this process. A computer window, mouse, cloud, stream and virus all reuse familiar words because the old concept offers a way to understand the new one.
Metonymy: association rather than resemblance
In metonymy, a word shifts through close association. The Crown can refer to the state or monarch’s authority; the press can refer to news media; the stage can refer to theatrical performance. The object, place or instrument comes to stand for the institution or activity connected with it.
New contexts create new senses
A word does not need to abandon its old meaning to gain a new one. Broadcast described scattering seed widely before it became a term for transmitting radio and television, and later digital content. The agricultural sense and media sense are historically linked, but modern speakers can use one without consciously invoking the other.
Most dictionary entries therefore contain multiple senses rather than a single definition that has simply replaced everything before it.
Euphemism and social pressure
Communities often replace a word considered blunt, offensive or distressing with a softer expression. Over time, the new expression may acquire the same negative associations because attitudes towards the underlying subject have not changed. This recurring pattern is sometimes called the euphemism treadmill.
The lesson is that changing vocabulary can improve respect and precision, but language alone cannot remove the social judgement attached to a concept.
Grammar can reshape meaning
Frequently used words can also develop grammatical functions. A verb of movement, intention or possession may gradually become part of a future, obligation or aspect construction. This process, known as grammaticalisation, shows that change affects not only definitions but the structure of sentences.
Do not commit the etymological fallacy
The etymological fallacy is the belief that a word’s oldest meaning is its only true meaning. History explains how a word arrived; current usage determines what it means now. Awful once related more directly to inspiring awe, but modern speakers are not mistaken when they use it to mean very bad.
Meaning belongs to communities
Semantic change is not decay. It is evidence that speakers are adapting language to new technologies, relationships, institutions and values. Dictionaries record that movement. They do not freeze words at their point of origin; they show the different work those words have come to do.
Meaning change is not linguistic decay
Some changes will irritate you, just as older changes irritated earlier speakers. The useful editorial question is not whether a sense is historically pure, but whether it is established, appropriate for the audience and clear enough in the sentence.